You need to send a sensitive PDF — a contract, financial document, legal material. Email feels risky. You want to protect the content.
What's actually going wrong
Standard email is not secure by default. Messages can be intercepted, forwarded, or read on stored servers. Attachments inherit the same risks.
Proper confidential sending means encrypting the file itself and controlling who can access it.
The quick fix
Encrypt the PDF before sending. Password protect PDF in Flint with a strong password. Email the encrypted file to the recipient. Send the password through a separate channel (text, phone call, in person) — never in the same email.
The encrypted attachment is useless without the password. Even if intercepted, the content stays protected.
If that didn't work
For ongoing sensitive exchanges, use secure sharing services with verified recipient identity — DocuSign, Tresorit, or enterprise document portals. These add audit trails and access logs.
For occasional sends, password-protected PDF via email with out-of-band password sharing is sufficient for most threat models.
For the most sensitive content, encrypted email services (ProtonMail, Tutanota) provide end-to-end encryption that even the email provider can't read.
Prevent it next time
Default to encryption for anything sensitive. Send passwords separately. Use end-to-end encrypted services for highest sensitivity. And limit confidential content to recipients you can verify.
FAQ
Is a password-protected PDF really secure?
With strong encryption (AES-256, which Flint uses) and a strong password sent separately, yes. Weak passwords or passwords sent in the same email defeat the protection.
What's a strong password for a PDF?
10+ characters, mixed case, numbers, symbols. Unique to that document. Memorable enough not to write down where it can be stolen.
Should I send the password via text?
Text is reasonably secure for the password (different channel from email). Phone calls, signal/whatsapp, or in-person are more secure. Never send password in the same email as the file.
What about recipients who can't handle encrypted PDFs?
Most viewers handle encrypted PDFs natively — the password prompt appears on open. For recipients unfamiliar with the process, walk them through it once.
Confidential sends start with encryption. Password protect in Flint and share the password separately.